Cancer is a term used to describe a group of malignancies that all share the common trait of developing when cells in a part of the body begin to grow out of control. Most cancers form as tumors, but can also manifest in the blood and circulate through other tissues where they grow. Cancer malignancies are most commonly treated with a combination of surgery, chemotherapy, and/or radiation therapy. The type of treatment used to treat a specific cancer depends upon several factors including the type of cancer malignancy and the stage during which it was diagnosed.
Busulfan is a commonly used cytotoxic agent that is used for the treatment of Chronic myelogenous leukemia and high-dose pre-transplant conditioning. This chemotherapeutic agent has the formula:

This compound has been associated with debilitating side effects such as mucositis, hepatic veno-occlusive disease and myelosuppression. By monitoring the levels of busulfan in the body and adjusting the dose these side effects can be better controlled and limited in patients.
At the same time, there is often high variable relationship between the dose of busulfan and the resulting serum drug concentration that affects therapeutic effect. The degree of intra- and inter-individual pharmacokinetic variability of busulfan can be as high as 10-fold (Slattery et. al. Blood 89(8): pp 3055–3060) and is impacted by many factors (Gurney et. al., J. Clin. Oncol. 14, pp 2590–2611, 1996), including:                Organ function        Genetic regulation        Disease state        Age        Drug-drug interaction        Time of drug ingestion,        Mode of drug administration, and        Technique-related administration.        
As a result of this variability, equal doses of the same drug in different individuals can result in dramatically different clinical outcomes (Hon et. al. Clinical Chemistry 44, pp 388–400, 1998). The effectiveness of the same busulfan dosage varies significantly based upon individual drug clearance and the ultimate serum drug concentration in the patient. Therapeutic drug management would provide the clinician with insight on patient variation in both oral and intravenous drug administration. With therapeutic drug management, drug dosages could be individualized to the patient, and the chances of effectively treating the cancer without the unwanted side effects would be much higher (Nieto, Current Drug Metabolism 2: pp 53–66, 2001).
In addition, therapeutic drug management of busulfan would serve as an excellent tool to ensure compliance in administering chemotherapy with the actual prescribed dosage and achievement of the effective serum concentration levels. It has been found that variability in serum concentration is not only due to physiological factors, but can also result from variation in administration technique.
Routine therapeutic drug management of busulfan would require the availability of simple automated tests adaptable to general laboratory equipment. Current testing for Busulfan involves gas chromatography/mass spectrometry (Slattery et. al., Bone Marrow Transplant 16: pp 31–42, 1995). GC/MS is labor intensive and expensive. Tests that would best fit the criteria of simplicity and availability are immunoassays. In order to be most effective in monitoring drug levels the antibody should be most specific to the active compound and display very low cross-reactivity to no cross-reactivity to the non-active blocking metabolites particularly tetramethylene sulfone, tetrahydrothiophene and tetrahydrothiophene-3-ol-1,1-dioxide [tetrahydro-3-thiophenol 1,1-dioxide].